Method, device and program for managing volume

ABSTRACT

Computer systems having a plurality of storage systems could not detect addition of storage systems or configuration changes thereof and automatically redistribute existing volumes based on “hints” provided when the volumes were created. A management computer, which is connected via a network to storage systems having volumes connected via a network to a host computer and which stores data used by the host computer, keeps correspondences between levels indicating specific performances of volumes and storage system characteristics indicating performances of the storage systems. From a first storage system, a level is obtained indicating a performance of a volume of the first storage system allocated to the host computer. The storage system characteristics of the first storage system corresponding to the obtained level indicating the performance of the volume, and storage system characteristics of another storage system are referenced, and the performances of the volumes of the storage systems are compared.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application relates to and claims priority from Japanese PatentApplication No. 2004-006214, filed on Jan. 14, 2004, and No.2004-066548, filed on Mar. 10, 2004, the entire disclosure of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a method of managing a volume in acomputer system that includes multiple storage subsystems.

In recent years, storage network structures have been used in whichmultiple servers, multiple storage subsystems, backup devices and thelike are connected by switches, hubs, etc. These are chiefly called SANs(Storage Area Networks). The advantages obtained by building a computersystem with a storage network include excellent scalability, and reducedadministrative costs are achieved by enabling integrated management ofdata that is dispersed across multiple storage subsystems.

Furthermore, when using large-scale storage subsystems—i.e., mostnotably for disk array subsystems—managing means are provided forcreating volumes to store information (i.e., data and programs) to beused by host computers inside the storage system. However, the managingmeans for creating the volumes use different interfaces and differentformats for making requests, depending on the vendor that created thestorage subsystem. Therefore, when a storage subsystem made by adifferent vendor is introduced to the system, the administrator of thestorage subsystems needs to be able to remember the interfaces andrequest the formats used by each vendor. In a large-scale scale computersystem, this causes significant problems. In order to overcome theseproblems, the DMTF (Distributed Management Task Force) has created a CIM(Common Information Model) and WBEM (Web-Based Enterprise Management).These standards determine the interface and request formats to be usedwhen creating a volume in a storage subsystem. For example,“Device27_StorageServices.mof v.2.7.1” in Device Storage Services 2.7was released. By using the interface defined in the CIM, a volume can becreated according to a uniform method even in storage subsystems made bydifferent vendors. The CIM definitions stipulate that “hints” are to beused in the interface and request formats when creating volumes.

(extracted from Device27_StorageServices.mof) //====================================================== //StorageSettingWithHints //====================================================== [Experimental,Version(“2.7.1”), Description (  “This subclass of StorageSetting allowsa client to specify ”  “‘hint's for optimization of the volumeperformance. The effect ”  “of these hints is implementationdependent.”) ] class CIM_StorageSettingWithHints: CIM_StorageSetting { [MinValue (0), MaxValue (10), Description (   “This hint is anindication from a client of the importance ”   “placed on dataavailability. Values are 0=Don't Care to ”   “10=Very Important.”) ] uint16 DataAvailabilityHint;  [MinValue (0), MaxValue (10), Description(   “This hint is an indication from a client of the randomness ”   “ofaccesses. Values are 0=Entirely Sequential to ”   “10=Entirely Random.”)]  uint16 AccessRandomnessHint;  [MinValue (0), MaxValue (10),Description (   “This hint is an indication from a client of thedirection ”   “of accesses. Values are 0=Entirely Read to ”  “10=Entirely Write.”) ]  uint16 AccessDirectionHint;  [Description (  “This hint is an indication from a client of the optimal ”   “accesssizes. Several sizes can be specified.”),   Units (“MegaBytes”) ] uint16 AccessSizeHint[];  [MinValue (0), MaxValue (10), Description (  “This hint is an indication from a client how important ”   “accesslatency is. Values are 0=Don't Care to ”   “10=Very Important.”) ] uint16 AccessLatencyHint;  [MinValue (0), MaxValue (10), Description (  “This hint is an indication from a client of bandwidth ”  “prioritization. Values are 0=Don't Care to ”   “10=Very Important.”)]  uint16 AccessBandwidthWeight;  [MinValue (0), MaxValue (10),Description (   “This hint is an indication of the importance the client”   “places on the cost of storage. Values are 0=Don't Care to ”  “10=Very Important. A StorageVolume provider might choose ”   “toplace data on low cost or high cost drives based on ”   “thisparameter.”) ]  uint16 StorageCostHint;  [MinValue (0), MaxValue (10),Description (   “This hint is an indication of the importance placed on”   “storage efficiency by the client. Values are 0=Don't Care ”   “to10=Very Important. A StorageVolume provider might choose ”   “differentRAID levels based on this hint.”) ]  uint16 StorageEfficiencyHint;};

Using these “hints” enables the volume to be made with abstractdesignations. This allows the volumes to be created with a uniformrequest format even when the hardware structure of each vendor's storagesubsystem is completely different.

Japanese Patent Application Laid-open No. 2003-140836 discloses a methodwhich is used to enable the distribution of a volume among multiplestorage subsystems in the SAN environment to be optimized easily byhaving the administrator redistribute the volume. This volume managementmethod is summarized as follows:

Multiple storage subsystems that are connected to a SAN environment areclassified into multiple groups (classes), or multiple disk devices thatconstitute the storage subsystems are classified into multiple groups(classes); and, for each of these classes, class attributes areconfigured (i.e., threshold values for usage of the storage subsystems).Either a SAN management server that is connected to the SAN, or a serverutilizing the volumes in the storage subsystems, obtains from themultiple storage subsystems vendor information indicating the vendor ofthe storage subsystem (i.e., manufacturer information), usage statusinformation, and class attributes. In order to redistribute the volumein a first class to an appropriate volume in a second class, the volumein the second class is selected based on the vendor information(manufacturer information), the usage status information, and the classattribute information. Then, data in the first volume is copied into thesecond volume, and the correspondence for keeping track of the volume ischanged from the first volume to the second volume to achieveredistribution.

In accordance with the volume redistribution method disclosed inJapanese Patent Application Laid-open No. 2003-140836, the volumemigrates across classes or within the same class based on the usagestatus information which is determined per class, the class attributes,and the storage subsystem's vendor information.

However, there is no disclosure of migrating a volume among the multiplestorage subsystems that are connected to the network. Furthermore, evenwhen each vendor's storage subsystems have different storage structures,the hints still enable the creation of volumes with uniform requestformats; however, even if the same values are defined for the hints,there are many cases where the properties that are actually exhibited bythe devices in correspondence to these values will be different indifferent storage subsystems produced by different vendors and the like.Therefore, when dealing with a volume that in multiple storagesubsystems, it is difficult for the administrator to use the hints as away to allocate the volumes to effectively utilize the resources.

SUMMARY OF THE INVENTION

The present invention has been made in light of the above-mentionedproblems, and it is therefore an object of this invention to enableeffective utilization of resources (volume) in multiple storage systemsby using levels (hints), which indicate the specific performances of thevolumes designated when the volumes are allocated.

In accordance with one embodiment for achieving the aforementionedobject of the present invention, a management computer, that isconnected via a network to storage systems having volumes connected viaa network to a host computer to store data used by the host computer,maintains a correspondence between a level indicating a specificperformance of a volume and storage system characteristics of thestorage system, obtains from a first storage system a level indicatingthe performance of a volume which the first storage system allocated tothe host computer, and references the first storage systemcharacteristics corresponding to the obtained level indicating theperformance of the volume and the storage system characteristics ofanother storage system, and compares the performances of the volumes ofthe respective storage systems.

Other characteristics of the present invention will become clear fromthe descriptions given in the present specification and from theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an outline of an embodiment of thepresent invention.

FIG. 2 is a block diagram showing a computer system in accordance withEmbodiment 1.

FIG. 3 is a diagram showing the format of a volume creation request.

FIGS. 4A and 4B are tables showing examples of storage subsystemcharacteristics.

FIGS. 5A to 5C are diagrams showing examples of volume informationpertaining to volumes in a first storage subsystem.

FIGS. 6A to 6D are diagrams showing volume management tables in a hostcomputer.

FIGS. 7A and 7B are diagrams showing volume information pertaining tovolumes in a second storage subsystem.

FIGS. 8A to 8B are diagrams showing setting screens for creating thevolumes.

FIG. 9 is a block diagram showing a computer system in accordance withEmbodiment 2.

FIGS. 10A to 10C are diagrams showing volume information pertaining tovolumes in a third storage subsystem.

FIG. 11 is a diagram showing a volume management table in a hostcomputer in accordance with Embodiment 2.

FIG. 12 is a block diagram showing the structure of a managementcomputer in accordance with an embodiment.

FIG. 13 is a flowchart representing a volume allocation program executedby the storage subsystem in accordance with an embodiment.

FIG. 14 is a flowchart representing a configuration collection programexecuted by the management computer in accordance with an embodiment.

FIG. 15 is a flowchart representing a volume creation program executedby a user in accordance with an embodiment.

FIG. 16 is a flowchart representing a volume evaluating program executedby the management computer in accordance with an embodiment.

FIG. 17 is a flowchart representing a volume migration program executedby the management computer in accordance with an embodiment.

FIG. 18 is a flowchart representing an external volume mapping programexecuted by the third storage subsystem in accordance with Embodiment 2.

FIG. 19 is a flowchart representing a volume access switching programexecuted by the management computer in accordance with Embodiment 2.

FIG. 20 is a diagram showing the hardware structure of volume migrationmeans in accordance with an embodiment.

FIG. 21 is a flowchart representing a volume copy program executed bythe volume migration means in accordance with an embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be explained in detailwith reference to the drawings.

OUTLINE OF EMBODIMENTS

FIG. 1 will be used to explain an outline of the embodiments forpracticing the present invention. In the computer system shown in FIG.1, a host computer 100, which uses storage space, is connected to astorage subsystem 301 and a storage subsystem 302 through a data network200; and a management computer 600, which manages the storage subsystem301 and the storage subsystem 302, is connected to the storagesubsystems 301, 302 through a management network 500.

In the system configuration shown in FIG. 1, the computer system (whichis constituted of the host computer 100, the storage subsystem 301 andthe management computer 600) also has the additional storage subsystem302 added thereto. (This is a variant configuration.) Furthermore, thedata network 200 is provided with volume migration means 700 fortransferring data between volumes. The volume migration means 700 isalso connected to the management network 500 so that it can receivetransfer requests from the management computer 600.

When the management computer 600 detects the addition of the storagesubsystem 302 (10), the management computer 600 then obtains storagesubsystem characteristics and a “hint” from the storage subsystem 301and from the storage subsystem 302, respectively (12). The managementcomputer 600 then reevaluates the storage subsystem characteristics andthe hints. If creating the volume in the newly added storage subsystem302 would enable a volume that is closer to the hint, then the “hint”that is associated with that volume is used to create a volume in thestorage subsystem 302 (14), and then the data in the volume in thestorage subsystem 301 is transferred to the newly created volume in thestorage subsystem 302 using the volume migration means 700. Finally, themanagement computer 600 sends a notification to the host computer 100 toindicate that the volume has been migrated and the host computer 100 isconfigured so as to reference the volume in the storage subsystem 302 onsubsequent occasions (18). This enables the host computer to use thevolume that more closely matches the “hint”.

Embodiment 1

(1) System Structure

FIG. 2 shows a system structure in accordance with Embodiment 1. In thecomputer system shown in FIG. 2, the host computer 100, which uses thevolume, is connected to the storage subsystem 301 and the storagesubsystem 302 through the data network 200; and the management computer600, which manages the storage subsystem 301 and the storage subsystem302, is connected to the storage subsystem 301 and the storage subsystem302 through the management network 500. In the system shown in FIG. 2,the computer system (which is constituted of the host computer 100, thestorage subsystem 301 and the management computer 600) has the storagesubsystem 302 added to it. (This is a variant construction.)Furthermore, the data network 200 is provided with the volume migrationmeans 700 for transferring data among the volumes. The volume migrationmeans 700 is connected to the management network 500 so that it canreceive data transfer requests from the management computer 600. In thepresent embodiment, the data network 200 is a fiber channel and themanagement network 500 is an IP (Internet Protocol) network. The datanetwork and the management network are not restricted to the abovedescriptions. Furthermore, the data network and the management networkcan be a different network or the same network.

Host Computer

The host computer 100 is constituted of:a CPU 105 for governingexecution of programs; a memory 110 for storing programs and datanecessary for execution of programs; a fiber channel interface (below,abbreviated as “FC interface”) 120 for connecting to the data network200 and executing exchanges of data between the storage subsystem 301and the storage subsystem 302; and a network interface 130 forconnecting to the management network.

The host computer 100 is capable of storing data generated by executionof the programs into the volumes of storage subsystems connected to thedata network 200 via the FC interface 120. Furthermore, the hostcomputer 100 can obtain the programs themselves and the data necessaryto execute the programs from the volumes in the storage subsystems viathe FC interface 120.

A volume management table 115 (see FIG. 6) is provided inside the memory110 of the host computer 100. The volume management table 115 manageswhich volume in which storage subsystem corresponds to the volume thatis being used by the application on the host computer 100 via the filesystem. In accordance with the present embodiment, the volume managementtable 115 is identified by means of a drive letter allocated to thevolume, an FC interface number and a volume number. A WWN (World WideName) is generally used as the FC interface number. Furthermore, a LUN(Logical Unit Number) determined by an SCSI (Small Computer SystemInterface) is generally used as the volume number. In the presentembodiment, in order to simplify the correspondence to the drawings,explanations will be given using the numbers that are used in thediagrams themselves instead of the WWN and the LUN numbers. The hostcomputer 100 reads out data from the volumes and writes data into thevolumes in accordance with the volume management table 115. The presentembodiment is constructed such that the volume management table 115 canbe rewritten from the management computer 600 through the networkinterface 130.

Storage Subsystems

A structure for the storage subsystems will now be explained. Thestorage subsystems 301, 302 have: a CPU 350 for governing execution ofprograms; a memory 360 for storing programs and information necessaryfor executing programs; a network interface 390 for executingcommunications with the management computer 600; FC interfaces(3711-3716, 3721-3729) for executing exchanges of data with the hostcomputer 100; a volume access control module 380 for processing dataread/write requests from the host computer 100; a cache 389 fortemporarily storing data received from the host computer 100 and dataread from the volumes; and volumes 3411, 3412 for actually storing thedata.

In the storage subsystem, the volumes which have already been allocatedand the volumes which are not yet allocated are managed by means of thevolume information on the volumes that are already allocated to the hostcomputer, managed by the volume access control module 380 . Inaccordance with the present embodiment, the storage subsystem 301 storesvolume information 383, and the storage subsystem 302 stores volumeinformation 384.

The memory 360 holds the storage subsystem characteristics 325 and thevolume information 382, and it has a volume allocation program 330 forallocating the volumes in accordance with a volume creation request fromthe management computer 600. This program is stored on a ROM, a magneticdisk, or other nonvolatile storage medium inside the storage subsystem,and, when the storage subsystem is booted, the program is loaded intothe memory 360 and is executed. Alternatively, the processes performedwith the program can also be achieved by means of hardware constructionsinside the storage subsystem.

A difference between the storage subsystems 301 and 302 is the bandwidthand quantity of the FC interfaces. The storage subsystem 301 has six FCinterfaces: FC interfaces 3711-3713 with bandwidths of 1 Gbps, and FCinterfaces 3714-3716 with bandwidths of 2 Gbps. The storage subsystem302 has nine FC interfaces: FC interface 3721-3723 with bandwidths of 1Gbps, FC interfaces 3724-3726 with bandwidths of 2 Gbps, and FCinterfaces 3727-3729 with bandwidths of 10 Gbps.

FIG. 3 shows an example of the parameters which are contained in thevolume creation request which the management computer 600 issues to thestorage subsystem. In accordance with the present embodiment, theparameters include four hints: how much capacity the volume that will becreated should have; an AccessBandwidthHint (ABH) indicating howstrongly a broad bandwidth is desired for the bandwidth for accessingfrom a host; a StorageCostHint (SCH) indicating how strongly aninexpensive bit unit price is desired for the bits constituting thevolume in the storage subsystem; and a DataAvailabilityHint (DAH)indicating how strongly a highly available volume is desired for thevolume.

Of these four hints, three will be used to explain the presentembodiment: ABH, SCH and DAH. A value between 1 and 10 is allocated toeach of these hints to allocate a level within a ten-level range. Thislevel indicates how important it is that the volume has the performanceindicated by each hint. For example, level “0” can mean “Don't care”,meaning that the hint in question is not considered important. In thiscase, the volume performance indicated by the given hint will be set toa low level in the respective storage subsystem. The given hint isconsidered to be more important as the number indicating the levelincreases. Level “10” indicates that the given hint is considered mostimportant, and the volume performance corresponding to that hint will bethe best that the storage subsystem can provide. In the presentembodiment, examples of the types of hints defined by the DMTF(Distributed Management Task Force) for the CIM (Common InformationModel) are used. However, other hints defined by the CIM and hints notdefined by the CIM can also be used to achieve the present embodiment.

FIGS. 4A and 4B illustrate tables which show correspondences between thehints and each type of storage subsystem characteristics in accordancewith the present invention. In a storage subsystem characteristics table325, the storage subsystem 301 holds the storage subsystemcharacteristics 326 shown in FIG. 4A, and the storage subsystem 302holds the storage subsystem characteristics 327 shown in FIG. 4B. Thestorage subsystem characteristics 326 indicate that the storagesubsystem 301 can provide a volume at a bandwidth of 1 Gbps or 2 Gbps,with a bit unit price of 1 ¢/MB, with 99.9% availability. The storagesubsystem characteristics 327 indicate that the storage subsystem 302can provide a volume at a bandwidth of 1 Gbps or 2 Gbps or 10 Gps, witha bit unit price of 2 ¢/MB, with 99.999% availability.

The bit unit price is determined based on the storage subsystem'spurchase price and purchasable amount. Therefore, in the presentembodiment, a different value is allocated to each storage subsystem.Furthermore, the availability also is determined by the structure of thedevice's hardware (i.e., whether or not the storage subsystem has aredundant and/or hot-swappable power source and controller). Therefore,in the present embodiment, a different value is allocated to eachstorage subsystem. The storage subsystem characteristics 326, 327 alsoindicate that the hint levels can be changed without changing the volumethat has been allocated. Since the bandwidth can be changed by changingthe FC interface settings and the settings of a bandwidth controller, itis also possible to create volumes having different settings within thestorage subsystem. In the storage subsystem 301, the AccessBandwidthHintcan be set to 1-5 to create a volume with a bandwidth of 1 Gbps, and theAccessBandwidthHint can be set to 6-10 to create a volume with abandwidth of 2 Gbps. If the hint level is 1, for example, then a greatervalue of 6 can indicate that the bandwidth for accessing the volume isgreater, meaning that a volume with a better access bandwidthperformance can be provided for the host computer. In the storagesubsystem 302, the AccessBandwidthHint can be set to 1-5 to create avolume with a bandwidth of 1 Gbps, the AccessBandwidthHint can be set to6-8 to create a volume with a bandwidth of 2 Gbps, and theAccessBandwidthHint can be set to 9-10 to create a volume with abandwidth of 10 Gbps. In the storage subsystems, volumes havingdifferent bandwidths can be provided to the host computer by changingthe FC interface for the newly created volume.

The present embodiment includes an example in which the hint levelvalues are different, but the storage subsystem characteristics indicatethe same performance values and performances. However, the storagesubsystem characteristics can also be set to different values for eachhint level.

Management Computer

FIG. 12 is a diagram showing the construction of the management computerin accordance with Embodiment 1. The management computer 600 is providedwith: a CPU 650 for governing execution of programs; a memory 660 forstoring programs and data necessary for executing programs; a display680 for displaying program execution status; a keyboard 682 and a mouse684 for inputting instructions from an administrator; and a networkinterface 690 for connecting to the management network.

The memory 660 in the management computer 600 has: a configurationcollection program 605 for obtaining storage subsystem characteristicsand volume information from the storage subsystem; a volume creationprogram 610 for creating the volume in the storage subsystem; a volumeevaluating the program 622 for evaluating volume in a case where a newstorage subsystem has been added; and a volume migration program 624 formigrating a volume from one storage subsystem to another storagesubsystem based on evaluation results produced by the volume evaluatingprogram 622. Although it is not shown in the diagrams, the memory 660holds the storage subsystem characteristics and the volume informationobtained from the storage subsystems and the volume management tableobtained from the host computer. A volume migration program 630 will beexplained in connection with Embodiment 2.

The programs are stored on a ROM, a magnetic disk or other nonvolatilestorage medium inside the management computer 600, and, when themanagement computer is booted, the programs are loaded into the memory360 and are executed. The processes achieved by the program can also beachieved by means of hardware constructions inside the managementcomputer.

(2) Details of Volume Allocation Processing Performed By StorageSubsystem

Next, an explanation will be given regarding the processing performed bythe storage subsystem using the volume allocation program 330. FIG. 13shows a flowchart of the volume allocation program 330. When the volumeallocation program 330 receives a volume creation request from themanagement computer 600 (step 13010), the volume information being heldin the volume configuration table 382 gets updated (step 13020). Morespecifically, the requested capacity is sectioned off from theunallocated volume and is allocated to the host computer (step 13025).Also, an unused FC interface having the value indicated in theAccessBandwidthHint is retrieved from among the unused FC interfaces,and the number of this FC interface is registered into the volumeinformation. Then, the value of the hint that was received is registeredinto the volume information. After performing step 13025, a notificationis then sent out to indicate that the volume information being held inthe volume configuration table 382 has been updated (step 13030). Thisnotification is sent out to the volume access control module 380 and tothe management computer 600. This notification causes the volume accesscontrol module 380 to reference the volume information and connect tothe FC interface to which the newly created volume was allocated.Furthermore, this notification also lets the management computer 600know that the volume allocation is complete.

FIGS. 5A to 5C show examples of the volume information. FIG. 5Aindicates that a volume 3412 is already allocated to the FC interface3714, and that it has a capacity of 200 GB and a bandwidth of 2 Gbps. Italso indicates that the hints received when the volume was allocatedindicated “10” for the AccessBandwidthHint, “0” for the StorageCostHint,and “10” for the DataAvailabiltyHint.

(3) Outline of Processing Performed by Management Computer 600

An explanation will now be given regarding an outline of the processingperformed by the management computer 600 in accordance with the presentembodiment. In the present embodiment, the management computer 600performs processing according to the following sequence.

First, the management computer 600 performs processing to obtain thesystem information from the storage subsystem 301, and it performsprocessing to give instructions to create the volume in the storagesubsystem 301. Then, it performs processing to detect the storagesubsystem 302 that has been newly added. Finally, it performs processingto give instructions to reevaluate and transfer the volume.

The above-mentioned processing is achieved by the following threeprograms. Namely, it involves the configuration collection program 605for detecting the storage subsystem and obtaining the information; thevolume creation program 610 for giving instructions to create the volumein the storage subsystem, and the volume evaluating program 622 which isused to perform the processing to reevaluate the volume that was createdin the storage subsystem. An explanation will now be given regarding theflow of these programs.

(3-1) Processing to Obtain Configuration Information

FIG. 14 shows a flowchart representing the configuration collectionprogram 605 that is executed by the management computer 600. First, themanagement computer 600 detects the storage subsystem that is connectedto the management network 500, and it obtains the storage subsystemcharacteristics (step 14010). More specifically, it sends out a storagesubsystem characteristics request over the management network 500 atgiven chronological intervals. The storage subsystem(s) send back thestorage subsystem characteristics in response to the storage subsystemcharacteristics request. When this occurs, the management computer 600has detected the storage subsystem. The storage subsystemcharacteristics that were sent back are held in the memory 660 so that,when volumes are created on future occasions, the information can beused to judge which storage subsystem the volume should be created in.After performing step 14010, the management computer 600 obtains thevolume information (step 14020). More specifically, it emits the volumeinformation request to the detected storage subsystem at givenchronological intervals, and then holds the volume information that isreturned in the memory 660.

The present embodiment will first be explained with respect to the casewhere only the storage subsystem 301 is connected. When the managementcomputer 600 executes the configuration collection program 605, thestorage subsystem characteristics 326 are received from the storagesubsystem 301.

(3-2) Processing to Create the Volume

Volume Creation Program 610, and Concrete Example 1 Employing VolumeCreation Program 610

FIG. 15 shows a flowchart of the volume creation program 610 that isexecuted by the management computer 600. A concrete example of theprocessing in FIG. 15 will be explained with reference to FIG. 5, FIG. 6and FIG. 8. The CPU of the management computer 600 executes the volumecreation program 610, which is stored in the memory 660.

First, the management computer 600 creates the volume creation request(step 15010). More specifically, the administrator uses the display andthe keyboard to input the target storage subsystem where the volume isto be created, the host computer which will use the volume, and theparameters of the volume creation request.

Examples of the input screens are shown in FIGS. 8A and 8B. A settingsscreen 800, such as shown in FIG. 8A, for creating the volume isdisplayed on the display 680 of the management computer 600. Thesettings screen 800 has six fields (810, 812, 818, 820, 822, 824). Theadministrator makes the following inputs as parameters in the volumecreation request: a host computer that can read and write data to andfrom the volume is inputted into a host computer input field 810; thedesired volume capacity is inputted into a capacity input field 812; thedesired storage subsystem number is inputted into a storage subsysteminput 818; and desired hints are inputted into the hints 820, 822, 824.Then the administrator presses a create button 830. By performing theseoperations, the volume creation request can be created in accordancewith the volume creation request parameters that were inputted.

For example, in order to create a volume characterized by high speed andhigh availability, where cost is not an issue, the administrator wouldinput “100” into the host computer input field 810, “200(GB)” into thecapacity input field 812, “301” into the storage subsystem input field818, “10” into the AccessBandwidthHint input field 820, “0” into theStorageCostHint input field 822, and “10” into the DataAvailabiltyHintinput field 824, and then the administrator presses the create button830. By performing this operation, the volume creation request iscreated in accordance with the inputted volume creation requestparameters. Returning to FIG. 15, an explanation will now be givenregarding the volume creation program 610.

Next, the management computer 600 sends the volume creation request thatwas created at step 15010 to the storage subsystem designated by thevolume creation request that was created at step 15010 as describedabove (step 15020).

After performing step 15020, the storage subsystem 301 receives thevolume creation request from the management computer 600 and executesthe volume allocation program 330 described above. More specifically, a200 GB volume 3412 is sectioned off according to the creation request;and, since the AccessBandwidthHint is “10”, the storage subsystemcharacteristics 326 are referenced and the volume 3412 is allocated tothe unused 2 Gbps FC interface 3714, and then the volume information 383is updated, as shown in FIG. 5A. The volume that is created here has abandwidth of 2 Gbps and a bit unit price of 1 ¢/MB, With 99.9%availability. Furthermore, the fact that the hint level for theStorageCostHint is “0” and the AccessBandwidthHint and theDataAvailabilityHint are “10” means that the cost is not an issue (costis not considered important) in the volume, but the volume has goodbandwidth and availability (bandwidth and availability are consideredimportant).

When the management computer 600 receives the notification from thestorage subsystem indicating that the allocation of the volume iscomplete, the management computer 600 then obtains the volumeinformation 383 that was updated with respect to the storage subsystemwhere the volume was created (step 15030).

Finally, the management computer 600 sends out a request to the hostcomputer designated step 15010 described above, to request an update ofthe volume management table, because the creation of the volume is nowcomplete (step 15040). For example, the management computer 600 mayinstruct the host computer 100 to update the volume management table 115so that it looks like FIG. 6A. When the host computer 100 receives theseinstructions, it updates the volume management table 115, and thisenables the host computer 100 to use the volume 3412 inside the storagesubsystem 301 as its “C” drive via the FC interface 3714. The foregoingexplanations describe the volume creation program 610.

The settings screen 800 shown in FIG. 8A for creating the volume mayalso be configured as a settings screen 801, which is shown in FIG. 8B.A difference between the settings screens 800 and 801 will be explainednext. In the settings screen 800, in order to allocate a volume to agiven host computer, individual administrators have to define all sixinput fields, including the storage subsystem and the three hints. Butthis requires the administrators to have sophisticated and extensiveknowledge regarding the storage subsystem where the volume is to becreated, and regarding the hints. Furthermore, in a case where multipleadministrators divide the work of managing multiple storage subsystemsand multiple host computers, there is a chance that each of theadministrators will designate the storage subsystems and the hintsaccording to his or her own standard, and that there will thus be nouniform standard for creating volumes across the system as a whole. Whenthe settings screen 801 is used, the administrator who is thoroughlyfamiliar with the system structure defines a “volume policy” in advance,which is a combination of a storage subsystem where volumes arefrequently created and the hint values. This volume policy is thenstored into the management computer 600. The individual administratorsdesignate three input fields: the host computer input field 810, thecapacity input field 812, and a volume policy selection field 816. Whenthe administrators designate these three input fields, they canreference the “volume policy” pre-stored in the management computer 600to obtain six inputs equivalent to the settings screen 800 describedabove. The settings screen 801 enables the administrators to reduce theburden of making inputs to create the volume.

By way of example, the volume policy could be one that places importanceon achieving low costs, or places importance only on the accessbandwidth. A volume policy that places importance on achieving low costscould define the StorageCostHint as “10”, and the other hints could bedefined as “0”, and this could be stored in the memory of the managementcomputer 600 as the volume policy defined for a specific storage. Avolume policy that places importance only on the access bandwidth coulddefine the AccessBandwidthHint as “10”, and the other hints could bedefined as “0”, and this could be stored similarly in the memory 660 asthe volume policy defined for a specific storage subsystem.

Concrete Example 2 Employing Volume Creation Program 610

As another specific example of how to apply the volume creation program610, explanations will now be given regarding the processing forcreating another volume in the storage subsystem 301.

This example similarly uses the settings screen 800 shown in FIG. 8A,which is used for creating the volume. The value “100” is inputted intothe host computer input field 810. The description “200(GB)” is inputtedinto the storage subsystem capacity input field 812. The value “1” isinputted into the AccessBandwidthHint input field 820, the value “10” isinputted into the StorageCostHint input field 822, the value “0” isinputted into the DataAvailabilityHint input field 824, and then theadministrator presses the create button 830. This causes the managementcomputer to create the volume creation request in accordance with theinputted parameters and to send the volume creation request to thestorage subsystem 301.

When the storage subsystem 301 receives the volume creation request, itsections off the requested 200 GB volume. Since the AccessBandwidthHintis defined as “1”, the volume information 383 is updated, as shown inFIG. 5B, so that the unused FC interface 3711 with 1-Gbps bandwidth getsallocated. The volume thus created will have a bandwidth of 1 Gbps and abit unit price of 1 ¢/MB, with 99.9% availability. Furthermore, sincethe StorageCostHint is “10” and the AccessBandwidthHint is “1”, it isclear that the cost is given a higher priority than the bandwidth. Sincethe DataAvailabiliytHint is “0”, it is also clear that little importanceis allocated to the availability.

When the allocation of the volume is complete, the management computer600 sends out instructions to the host computer 100 to update the volumemanagement table 115 as shown in FIG. 6B. By updating the volumemanagement table 115, the host computer 100 becomes able to use thevolume 3411 in the storage subsystem 301 as its “D” drive via the FCinterface 3711.

(3-3) Processing to Detect New Storage Subsystem

Next, an explanation will be given regarding the processing performed bythe management computer 600, which is undertaken in the case where thestorage subsystem 302 is added to the computer system after two volumeshave already been created in the storage subsystem 301. In the presentembodiment, when the storage subsystem 302 is added to the computersystem, the FC interfaces 3721-3729 are connected to the data networkand the network interface 390 is connected to the management network.

At given chronological intervals, the management computer 600 executesstep 14010 of the configuration collection program 605, which has beendescribed above. Then, when the storage subsystem 302 has been added tothe computer system, the processing is performed to detect the storagesubsystem 302, which is connected to the network interface 690 of themanagement computer 600 via the management network 500. This enables thestorage subsystem characteristics of the storage subsystem 302 and thevolume information to be obtained. The management computer 600 holds theobtained storage subsystem characteristics in the memory 660 so that onsubsequent occasions it can be used to judge which storage subsystem tocreate the volume in when performing the processing to create thevolume.

(3-4) Processing to Reevaluate and Transfer the Volume

After detecting the new storage subsystem, the management computer 600begins the volume evaluating program 622 to evaluate the volumes thathave already been allocated. Reevaluation refers to referencing thestorage subsystem characteristics of the newly added storage subsystemand the volume information of the other storage subsystem(s), and tojudging which storage subsystem can provide the volume that best matchesthe hints. If one can be provided, then the hint information is used toactually create the volume in the newly added storage subsystem, and totransfer the data that is being held in the volume. This enables thevolume that matches the hint better to be provided to the host computer.Below, an explanation will be given regarding the volume evaluatingprogram 622, which is executed by the management computer 600 in thebeginning, and then a detailed explanation will be given regarding aconcrete example of how to apply the volume evaluating program 622 inaccordance with the present embodiment.

Explanation of Flow of Volume Evaluating Program 622

FIG. 16 shows a flowchart representing the volume evaluating program 622that is executed by the management computer 600.

The management computer 600 uses the above-mentioned configurationcollection program 605 to obtain the latest system information.

The processing from step 16030 to step 16130 is executed on all thevolume information entries obtained from all the storage subsystems(step 16020).

First, a volume information entry which has not yet been processed isselected (step 16030).

Then, the processing of step 16050 to step 16090 is executed on all ofthe hint information defined in the volume information entry that hasbeen selected (step 16040).

First, hint information which has not yet been processed is selected(step 16050).

For the selected hint information, the value for the hint information ofthe currently selected volume information entry is used to obtain thestorage subsystem characteristics corresponding to the values for thehint information of all of the storage subsystems (step 16060). Morespecifically, by using, as a key, the combination of the hintinformation of the currently selected volume information entry and thevalue for the hint information, the storage subsystem characteristics ofall the storage subsystems can be retrieved, and the storage subsystemcharacteristics that are provided with this hint value can be obtained.

After that, the storage subsystem characteristics received at step 16060are compared to determine whether there is a storage subsystem which canprovide a volume with a better performance than the storage subsystemwhich the storage subsystem characteristics entry that is currentlyselected belongs to (step 16070).

At step 16070, if there is a storage subsystem providing a volume with abetter performance, then one can expect that the volume performancewould be improved by migrating the volume from the storage subsystemwhere the volume currently is located, to the storage subsystemproviding the volume with the better performance. Therefore, the storagesubsystem providing the volume with the better performance becomes atransfer destination candidate (step 16080). Here, if multiple storagesubsystems can provide volumes with a better performance, the transferdestination candidate can be only the storage subsystem providing thevolume with the best performance, or, alternatively, all of the storagesubsystems can become transfer destination candidates. Furthermore, evenwhen multiple storage subsystems can provide superlative performance,the management computer 600 can freely select one subsystem of thestorage subsystems as the transfer destination candidate, or,alternatively, all of the storage subsystems can become transferdestination candidates.

At step 16070, if there is no storage subsystem providing a volumeoffering a better performance, then there is no transfer destinationcandidate for the currently selected hint information. Finally,processing on the selected hint is considered complete (step 16090) andthen the procedure returns to step 16040.

After step 16040 is repeated to perform the processing on all of thehint information, the management computer 600 determines which storagesubsystem will serve as the volume transfer destination (step 16100).Here, the following methods can be used to determine the storagesubsystem which is to be used to serve as the volume transferdestination. The management computer 600 can freely select a storagesubsystem from among all of the storage subsystems that became transferdestination candidates through the repeated execution of step 16040. Or,information pertaining to all of the transfer destination candidatestorage subsystems can be outputted on the display 680, and theadministrator can make a selection. Or, the administrator can assigndefinitions in advance to assign weights to the hint information, and astorage subsystem which is a transfer destination candidate can beselected with priority over the others because of one of the hints. Onthe other hand, there are also cases where the storage subsystem(s)selected as the transfer destination(s) would offer an improvement inperformance with respect to a certain hint, but would not offer animprovement with respect to another hint. For example, the accessbandwidth may be improved, but availability may suffer. In this type ofcase, a dialogue box can be displayed to the administrator to confirmwhether the volume may be migrated, or, alternatively, the followingsteps can be performed without asking the administrator to provideconfirmation.

After determining which storage subsystem at step 16100 is to serve asthe volume transfer destination, the management computer 600 transfersthe volume (step 624).

After performing step 624, the processing on the selected volumeinformation is considered complete (step 16130), and then the procedurereturns to step 16020.

The foregoing explanations have described the volume evaluating program622.

Explanation of Flow of Volume Migration Program 624

FIG. 17 shows a flowchart representing the volume migration program 624,which is executed by the management computer 600 after performing step16100 of the volume evaluating program 622.

First, the management computer 600 judges whether or not the originalvolume is utilizing an external volume mapping program (step 17010). Theexternal volume mapping program will be described below in connectionwith Embodiment 2. In the present embodiment, “NO” is assumed to be theresult of the judgment performed here.

Next, the management computer 600 judges whether or not the originalvolume has been registered in the host computer (step 17020).Specifically, this judgment can be performed as follows: a volumemanagement table request can be sent out over the management network,and then, from among all of the volume entries in the volume managementtables from all of the host computers that provide responses, an entrycan be extracted which has the same volume number as the volume numberof the volume being migrated.

If there is a host computer using the volume at step 17020, then themanagement computer 600 gives instructions to all of the host computerswhere the volume being migrated is registered, so that the volume whichis being migrated and which is in the volume management table in eachhost computer is changed to indicate that it is being migrated (step17030). More specifically, a migration flag, which is in the volumemanagement table 115 of the given host computer and which is used forthe volume entry, is changed from “0” to “1”. The host computerreferences the migration flag in the volume management table 115 eachtime it accesses the volume, and this suppresses access during thevolume transfer processing.

In a case where the original volume was using the external volumemapping program at step 17010, and in a case where the original volumewas not registered in the host computer at step 17020, and after step17030 is performed, the management computer 600 creates a new volume inthe storage subsystem where the volume will be migrated to. A detailedexplanation of this step is omitted because it is similar to the volumecreation program 610 described above.

After the new volume is created in the storage subsystem that was chosenas the volume transfer destination, the management computer 600 givesinstructions to the volume migration means 700 to transfer the data ofthe volume (step 17040). The volume is generally a 512-byte blockaggregate for storing data. Therefore, the management computer 600 hasonly to give to the volume migration means 700 the original storagesubsystem and volume number and the destination storage subsystem andvolume number, as parameters for the volume migration means 700. Thevolume migration means 700 uses the received parameters to copy the databetween the first block and the last block in the volume of the originalstorage subsystem into the destination storage subsystem and volume. Byway of example, the volume migration means of the present embodiment maybe a program that is executed on an independent host computer forreceiving the instruction parameters via the management computer 600 andthe IP network 500, and this program may be executed to achieve copyingbetween volumes via the fiber channel 200.

Similar to step 17010, the management computer 600 then searches to findout whether or not there is a host computer which is using the volumebeing migrated (step 17050). If a host computer is using the volume,then the management computer 600 gives instructions to that hostcomputer to update its volume management table (step 17060). Morespecifically, from the volume information of the destination storagesubsystem, the management computer 600 extracts a value representing thecurrent destination volume's FC interface number, and a valuerepresenting the volume number. These values are used to rewrite theentry for drive letters where the migration flag is “1”. Then themigration flag for the entry is changed from “1” back to “0”.

Finally, the management computer 600 releases the volume in the originalstorage subsystem (step 17070). Specifically, instructions are given tothe original storage subsystem to delete the original volume entry fromthe volume information.

The foregoing explanations have described the volume migration program624.

Specific Example Employing Volume Evaluating Program 622

In order to provide a specific example of how to apply the volumeevaluating program 622, a case will be described in which the storagesubsystem 302 is added to the computer system, when the storagesubsystem 301 has volumes 3411, 3412 in accordance with the presentembodiment. By connecting the storage subsystem 302, the managementcomputer 600 has two sets of storage subsystem characteristics 326, 327.Furthermore, the storage subsystem 302 does not have the volume alreadycreated inside it in its initial state.

First, by performing step 605, the management computer 600 obtains thesystem information from each of the storage subsystems connected to themanagement network 500. In the present embodiment, the informationobtained from the storage subsystem 301 is the storage subsystemcharacteristics 326 shown in FIG. 4A, and the volume information 383shown in FIG. 5B. On the other hand, the storage subsystem 302 hasneither the storage subsystem characteristics 327 shown in FIG. 4B, nora single volume. Therefore, the empty volume information 384 shown inFIG. 7A is obtained from it.

The management computer 600 then performs the evaluation from step 16020to step 16130 on the volume written in the volume information. Thepresent embodiment has two sets of volume information 383, 384. However,since the volume information 384 obtained from the storage subsystem 302is empty, processing is performed on the volumes 3412, 3411 which arewritten in the volume information 383 that was obtained from the storagesubsystem 301.

The management computer 600 first starts the reevaluation of the volume3412, which is in the first line of the volume information 383. Thefirst step of the reevaluation is to reference the value defined in thehint information AccessBandwidthHint for the volume 3412. The valuedefined for the AccessBandwidthHint is “10”. The management computer 600also references the bandwidth value defined for when theAccessBandwidthHint values for the storage subsystem characteristics 326and the storage subsystem characteristics 327 are both “10” (step16060). The bandwidth at the storage subsystem 301 is 2 Gbps, but thebandwidth at the storage subsystem 302 is 10 Gbps, which is highlyaccelerated. Therefore, since a high-performance volume can be provided(step 16070), the storage subsystem 302 is defined as the transferdestination candidate. The selected hint information is then consideredcomplete (step 16090), and the evaluation of the volume is performedusing the next hint information (step 16040).

Next, the value defined for the hint information StorageCostHint for thevolume 3412 is referenced. Since the value for the StorageCostHint is“0”, reevaluation does not need to be performed with respect to thishint.

Finally, the value defined for the hint information DataAvailabilityHintfor the volume 3412 is referenced. The value for theDataAvailabilityHint is defined as “10”. Then the management computer600 references the availability value defined for when the values of theDataAvailabilityHint of the storage subsystem characteristics 326 andthe storage subsystem characteristics 327 are both “10”. Theavailability of the storage subsystem 301 is “99.9%”, but theavailability of the storage subsystem 302 is “99.999%”. If the volume ismigrated to the storage subsystem 302, then the availability can beimproved. Since it is possible to provide a higher-performance volume(step 16060), the storage subsystem 302 is then defined as the transferdestination candidate. Then, the processing on the selected hintinformation is considered complete (step 16090), and all of the hitinformation in the volume information has been referenced, so that theevaluation of the volume ends.

The evaluation described above produces a judgment that the bandwidthand availability could be improved by migrating the volume 3412 from thestorage subsystem 301 to the storage subsystem 302.

Therefore, the volume evaluating program 622 then advances to step 16100and selects the storage subsystem 302 as the storage subsystem totransfer the volume to. At step 624, which is the volume migrationprogram 624, the transfer of the volume is started. In order to transferthe volume 3412, the management computer 600 judges that the volume 3412is not using the external volume mapping program, based on the volumeinformation of the storage subsystem 301 and the storage subsystem 302.Furthermore, the management computer 600 obtains the volume managementtable 115 from the host computer 100 and determines that the hostcomputer 100 is using the volume 3412. Therefore, an instruction isgiven to set the migration flag in the line for the volume 3412 in thevolume management table 115 to “1”, and thus the volume 3412 isconsidered to be in the process of getting migrated (FIG. 6C).

Next, the management computer 600 creates the volume creation requestbased on the hint and the capacity that were allocated to the volume3412, and then emits this request to the storage subsystem 302. When thevolume allocation program 330 for the storage subsystem 302 receives thevolume creation request, it then prepares the requested 200-GB volume3429. Since the AccessBandwidthHint is defined as “10”, the volumeinformation 384 is updated to look like FIG. 7B to allocate the unused10-Gbps FC interface 3727. The volume that is created here has abandwidth of 10 Gbps and a bit unit price of 2 ¢/MB, with 99.999%availability. When the creation of the volume 3429 in the storagesubsystem 302 is complete, the management computer 600 instructs thevolume migration means 700 to transfer the data inside the volume 3412in the storage subsystem 301 to the volume 3429 in the storage subsystem302. Once the data is completely copied into the volume 3429, themanagement computer 600 instructs the host computer 100 to update itsvolume management table 115, as shown in FIG. 6D (the migration flaggets returned to “0”). This causes the “C” drive of the host computer100 to become the volume 3429 connected to the FC interface 3727 of thestorage subsystem 302. Since the volume migration means 700 hastransferred the data in the volume 3412 to the volume 3429, the hostcomputer 100 can access the data without any changes to the volume 3412.

Finally, the management computer 600 emits a volume release request tothe storage subsystem 301 to have the volume 3412 be consideredunallocated. When the storage subsystem 301 receives the volume releaserequest for the volume 3412, the volume information 383 is updated, asshown in FIG. 5C. Accordingly, the volume 3412 and the FC interface 3714become free.

Next, the management computer 600 returns to step 16020 and startsreevaluating the volume 3411, which is in the second line of the volumeinformation 383 shown in FIG. 6B (steps 16030-16040).

First, the management computer 600 references the hint informationAccessBandwidthHint for the volume 3411. The value of theAccessBandwidthHint is “1”. Then, the management computer 600 referencesthe value defined for the bandwidth when “1” is the value of theAccessBandwidthHint for both the storage subsystem characteristics 326and the storage subsystem characteristics 327 (step 16060). Here it islearned that both of the storage subsystems offer bandwidths of 1 Gbps(step 16070). Therefore, the storage subsystem 302 does not become atransfer destination candidate. The processing on the hint informationis then considered complete (step 16090), and then the next hint valueis referenced (step 16020).

Next, the management computer 600 references the value or the hintinformation StorageCostHint for the volume 3411. The value of theStorageCostHint is “10”. The management computer 600 then references thevalue defined for the bit unit price when “10” is the value defined forthe StorageCostHint in both the storage subsystem characteristics 326and the storage subsystem characteristics 327. Thus, it is determinedthat the storage subsystem 301 has a bit unit price of 2 ¢/MB, and thestorage subsystem 302 has a bit unit price of 1 ¢/MB. In other words, ifthe volume is moved to the storage subsystem 302, the bit unit pricewill rise, and so the storage subsystem 302 is not a transferdestination candidate. Finally, the value defined for the hintinformation DataAvailabilityHint for the volume 3411 is referenced.Since the DataAvailabilityHint value is “0”, reevaluation is notnecessary with respect to this hint.

By the foregoing evaluation, it has been determined that there is notransfer destination candidate for the volume 3411, and, therefore,there is no benefit in migrating the volume from the storage subsystem301. Therefore, the management computer 600 does not transfer the volume3411. Since there is no other volume entry to select, the processing ofthe volume evaluating program 622 ends.

As explained above, in the present embodiment, the storage subsystem 302does not have the volume when it is in its initial state. However, evenwhen the storage subsystem 302 has a volume, the processing can beperformed as described above to reevaluate the volume inside the storagesubsystem 302 and transfer the volume appropriately in accordance withthe storage subsystem characteristics and the hint information.

Furthermore, as illustrated above, in the present embodiment, areevaluation is performed when the new storage subsystem is added andthe configuration collection program 605 detects the new storagesubsystem. However, it is also possible to perform the reevaluation in acase where a new storage subsystem has not been added, but where achange has occurred in the system information of an existing storagesubsystem. For example, the bit unit price can be changed when time haselapsed since purchase of the storage subsystem and the value of thehost computer has depreciated. When this approach is taken, the storagesubsystem characteristics can be changed automatically by the storagesubsystem itself or by the administrator. The configuration collectionprogram 605 can detect the change and execute the volume evaluatingprogram 622 to transfer the volume where the StorageCostHint isprioritized to a volume with a less expensive unit cost.

Furthermore, at given chronological intervals, or when prompted by aninput from a user, the management computer 600 can execute theconfiguration collection program 605 to obtain the system information.

The present embodiment was explained under the assumption that thestorage subsystem possesses a discriminating program in advance.However, in a case where the storage subsystem does not posses storagesubsystem characteristics, the administrator can use the managementcomputer to prepare the storage subsystem characteristics for a givenstorage subsystem. When the administrator has created (or modified) thestorage subsystem characteristics, the volume evaluating program 622 canbe executed to perform a reevaluation of the volume as described inconnection with the present embodiment.

Furthermore, in accordance with the present invention, thecorrespondence tables, such as shown in FIG. 4A and FIG. 4B are obtainedfrom the storage subsystems 301, 302 in the same format. However, inactuality, if the storage subsystems are provided by different vendors,then it is conceivable that the storage subsystems will use differentformats. In this case, a conversion program is made ready in themanagement computer to convert the formats of the correspondence tables,thus enabling the processing described in connection with the presentembodiment.

Also, in accordance with the embodiment, at step 16020 of the volumeevaluating program, the program is executed on the basis of the volumeinformation of all the storage subsystems connected to the managementcomputer via the network. However, the processing can also be performedon basis of the hint information for the volume information being heldin just one or more of the storage subsystems.

Embodiment 2

(1) System Structure

FIG. 9 shows a system structure in accordance with Embodiment 2.Embodiment 2 will be explained with respect to a case where a storagesubsystem 303 is added to the computer system having the storagesubsystem 301.

The differences between the present embodiment and Embodiment 1 will beexplained below.

A first difference is that, when the storage subsystem 303 is added inthe present embodiment, the storage subsystem 301 is removed from thedata network 200 and connected to the storage subsystem 303.

A second difference is that, in Embodiment 1, the volume migration means700 was connected to the data network 200, but in the present embodimentthe volume migration means 700 is provided within the storage subsystem303.

A third difference concerns the structure of the management computer 600shown in FIG. 12. The construction in the present embodiment uses thestructure from Embodiment 1, but also includes a volume access switchingprogram 630.

A fourth difference concerns the structure of the storage subsystem 303which is added in the present embodiment. Detailed explanations will nowbe given below.

The storage subsystem 303 has FC interfaces 3731-3736 to connect withthe storage subsystem 301. The FC interfaces 3731-3733 are 1 Gbps, andthe FC interfaces 3734-3736 are 2 Gbps.

Furthermore, the storage subsystem 303 has a function whereby it canprovide the volume in storage subsystem 301, which the storage subsystem303 can recognize, to the host computer 100 through the FC interfaces3731 to 3736, just as if it were the volume of the storage subsystem303. This function is possible because the volume access control module380 of the storage subsystem 303 has the volume information 385 shown inFIG. 10 to FIG. 10C. The volume information 385 shown in FIG. 10A toFIG. 10C is able to hold, in addition to the volume information as inEmbodiment 1, the FC interface numbers and volume numbers of an externalstorage subsystem where the external volume is stored (this is thestorage subsystem 301 in the present embodiment), while maintainingtheir correspondences with the volume information.

The storage subsystem 303 has three FC interfaces 3737-3739 forconnection to the data network 200, which is connected to the hostcomputer 100. The FC interfaces 3737 to 3739 are 10-Gbps FC interfaces.

The storage subsystem 303 also has an external volume mapping program340 that is held in the memory 360.

The foregoing explanations illustrate the differences between Embodiment2 and Embodiment 1.

In Embodiment 2, the storage subsystem characteristics held in thestorage subsystem characteristics table 325 shown in FIG. 9 is such thatthe storage subsystem characteristics of the storage subsystem 301corresponds to FIG. 4A, and the storage subsystem characteristics forthe storage subsystem 303 corresponds to FIG. 4B. Other constructions ofthe storage subsystem 303, which are not touched upon in Embodiment 2,are similar to those of Embodiment 1, as already described withreference to FIG. 2.

(2) Volume Allocation Program Executed By Storage Subsystem

In the present embodiment, the volume allocation program executed by thestorage subsystem is not different from that of Embodiment 1. Therefore,repeated explanations of this program are omitted.

(3) Details of Processing Performed by Management Computer 600

An explanation will now be given regarding details of the processingperformed by the management computer 600, in accordance with the presentembodiment. In the present embodiment, the management computer 600executes processing in the following sequence. First, it performsprocessing to obtain the system information from the storage subsystem301, and then performs processing to create the volume in the storagesubsystem 301. Then, processing is performed to connect the newlyconfigured storage subsystem 303 and the storage subsystem 301.Processing is also performed to detect the storage subsystem 303, and,finally, processing is performed to reevaluate and transfer the volume.

(3-1) Processing to Obtain Information

In the present embodiment, the configuration collection program 605,which the management computer 600 uses to obtain the information aboutthe storage subsystems, is similar to Embodiment 1. Therefore, anexplanation of this program is omitted.

In the present embodiment as well, it is conceivable that only thestorage subsystem 301 is connected at first, as in Embodiment 1.Therefore, when the management computer 600 executes the configurationcollection program 605, the storage subsystem characteristics 326 aresent from the storage subsystem 301.

(3-2) Processing to Create Volume

In the present embodiment, the volume creation program 610, which themanagement computer 600 uses to create the volume, is similar toEmbodiment 1. Therefore, an explanation of this program is omitted.

In the present embodiment as well, the management computer 600 is usedto create the volume 3411 and the volume 3412 in the storage subsystem301, as in Embodiment 1.

(3-3) Processing to Connect Storage Subsystem 301 and Storage Subsystem303

As described above, in the present embodiment, if the storage subsystem303 has been added to the system, then the processing to connect thestorage subsystem 301 and the storage subsystem 303 becomes necessary.This connection processing is performed in the following sequence.

First, the interface connection between the storage subsystem 301 andthe storage subsystem 303 is modified so that the storage subsystem 301system information and volume can be obtained from the storage subsystem303.

Then, the external volume mapping program 340 provided to the storagesubsystem 303 is executed to enable the host computer 100 to use thevolume in the storage subsystem 301 just as if it were the volume of thestorage subsystem 303.

Finally, the volume access switching program 630 provided to themanagement computer 600 is executed to modify the configuration suchthat the host computer 100 can use the volume in the storage subsystem303.

Details of each of these procedures will be explained below.

Modification of Connection to Storage Subsystem Interface

In the present embodiment, the storage subsystem 301 is removed from thedata network 200 and then connected to the storage subsystem 303. The FCinterfaces 3711-3713 of the storage subsystem 301 are connected to theFC interfaces 3731-3733 of the storage subsystem 303. The FC interfaces3714-3716 of the storage subsystem 301 are connected to the FCinterfaces 3734-3736 of the storage subsystem 303. In other words, FCinterfaces with bandwidths of 1 Gbps are connected to each other, and FCinterfaces with bandwidths of 2 Gbps are connected to each other, sothat the FC interfaces with the same bandwidths are connected to eachother. It is possible, however, to connect FC interfaces that havedifferent bandwidths. In this case, operations are performed at thesmaller bandwidth. Furthermore, the FC interfaces do not have to beconnected directly to each other; they can be connected to each othervia the data network 200.

The network interface 390 of the storage subsystem 303 is connected tothe management network 500.

Execution of the External Volume Mapping Program 340

First, an explanation will be given regarding the flow of the externalvolume mapping program 340.

FIG. 18 shows the flow of the external volume mapping program 340 thatis executed by the storage subsystem 303.

First, the storage subsystem 303 monitors the FC interfaces 3731-3736 atregular intervals to check whether a new storage subsystem has beenconnected (step 18010).

At step 18010, when a connection of a new storage subsystem is detected,the storage subsystem 303 then sends a request over the managementnetwork 500 to the storage subsystem that was connected and obtains thevolume information of that new storage subsystem(step 18020).

Finally, the storage subsystem 303 uses the volume information obtainedat step 18020 to update itself, i.e., the storage subsystem 303 (step18030). More specific descriptions are provided below. The storagesubsystem 303 may be configured to seek confirmation from theadministrator before performing this updating processing, but thepresent embodiment does not seek confirmation from the administrator.

The foregoing explanations have described the external volume mappingprogram 340.

Next, an explanation will be given regarding application of thisexternal volume mapping program 340 in accordance with the presentembodiment.

After completing the modification of the interface connection betweenthe storage subsystems, the storage subsystem 303 performs step 18010 tomonitor the FC interfaces 3731-3736 at regular intervals to checkwhether the storage subsystem has been connected.

When it has been confirmed that the storage subsystem 301 has beenconnected, the storage subsystem 303 performs step 18020 to obtain thevolume information 383 from the storage subsystem 301.

After obtaining the volume information from the storage subsystem 301,the storage subsystem 303 then performs the final step 18030 to updatethe volume information 385 that is stored in the storage subsystem 303itself. Specifically, the volumes 3411, 3412 in the storage subsystem301 are registered into the volume information 385 so they can beprovided to the host computer 100 just as if they were volumes of thestorage subsystem 303. FIG. 10A shows the volume information 385 afterbeing updated by step 18030. In FIG. 10A the volume 3431 which isprovided by the storage subsystem 303 is connected to the FC interface3737. A capacity of 200 GB is shown, which is similar to FIG. 5A. InFIG. 10A, the actual source of the volume in the storage subsystem 303is the same as in the external storage subsystem connected to thestorage subsystem 303. It therefore holds information about the externalstorage subsystem. For example, in the case of the volume 3431, it isclear that what is being used as the actual source of the externalvolume is volume number 3411 in the storage subsystem 301, which is theexternal storage subsystem connected to the FC interface number 3711.Similarly, the volume 3432 being provided by the storage subsystem 303is connected to the FC interface 3738, and its capacity is 200 GB.Furthermore, what is being used as the actual source of the externalvolume is volume number 3412 in the storage subsystem 301, which is theexternal storage subsystem connected to the FC interface 3714. In otherwords, the volume information 385 held in the storage subsystem 303includes: the volume number inside the storage subsystem 303 itself; thecapacity of that volume;the number and bandwidth of the FC interfaceconnected to that volume; the hint information pertaining to thatvolume; the volume number of the external volume in the correspondingexternal storage subsystem; and the number of the FC interface connectedto the external volume in the corresponding external storage subsystem.

Execution of the Volume Access Switching Program 630

First, the flow of the volume access switching program 630 will beexplained.

FIG. 19 shows the flow of the volume access switching program 630, whichis executed by the management computer 600.

First, the management computer 600 executes the configuration collectionprogram 605 and obtains the volume information for the storage subsystem(step 605).

Then, a request for the volume management tables in the host computersis distributed over the management network 500, and the volumemanagement table in each host computer is thus obtained (step 19020).

Finally, instructions are given to the host computers to update theirvolume management tables based on the volume information of the storagesubsystems and the volume management tables from the host computers,which were obtained at step 605 and step 19020 described above (step19030). Details of this step are described in the specific examples.

The foregoing explanations describe the volume access switching program630.

Next, an explanation is given regarding application of this volumeaccess switching program 630 in accordance with the present embodiment.

First, at step 605, the management computer 600 obtains the volumeinformation from the storage subsystem 301 and the storage subsystem303. More specifically, the volume information 383 shown in FIG. 5B isobtained from the storage subsystem 301, and the volume information 385as shown in FIG. 10A is obtained from the storage subsystem 303.

Next, at step 19020 the management computer 600 obtains the volumemanagement table from the host computer 100. Specifically, the volumemanagement table 115 shown in FIG. 6B is obtained from the host computer100.

Finally, at step 19030, the management computer 600 gives instructionsto the host computer 100 to update the volume management table 115. Morespecifically, using the volume information and the volume managementinformation in the volume management table 115 of the storage subsystem301, the management computer 600 first learns that the host computer 100was using the volume 3411 and the volume 3412 in the storage subsystem301. Then, using the volume information from the storage subsystem 301and from the storage subsystem 303, the management computer 600 learnsthat the content in the volume 3411 in the storage subsystem 301 isbeing provided from the storage subsystem 303 as the volume 3431, andthat the content in the volume 3412 of the storage subsystem 301 isbeing provided from the storage subsystem 303 as volume 3432. Therefore,the management computer 600 gives an instruction to the host computer100 to change the volume management table 115 from the content shown inFIG. 6B to the content shown in FIG. 11. Using the modified volumemanagement table 115 shown in FIG. 11, the host computer 100 cancontinue using the content in the volume 3411 and in the volume 3412 ofthe storage subsystem 301 in the same fashion, just as if they were thevolume 3431 and the volume 3432 in the storage subsystem 303.

(3-4) Processing to Detect New Storage Subsystem

In the present embodiment, the configuration collection program 605,which the management computer 600 uses to detect the storage subsystem303, is similar to Embodiment 1. Therefore, an explanation of thisprogram is omitted.

In the present embodiment as well, the management computer 600 detectsthe storage subsystem 303 and obtains the storage subsystemcharacteristics 327.

(3-5) Processing to Reevaluate and Transfer the Volume

Flow of Volume Reevaluation Program and Access Switching Program

In the present embodiment, the volume evaluating program 622, which themanagement computer 600 uses to reevaluate the volume, is similar tothat of Embodiment 1. Therefore, an explanation of the flow of thisprogram is omitted.

In the present embodiment, the volume migration program 624, which themanagement computer 600 uses to transfer the volume, is similar to thatof Embodiment 1. However, one difference is that there is thepossibility that at step 17010 the judgment will be made that theoriginal volume is using the external volume mapping program of thestorage subsystem 303. The following method can be used to make thisjudgment at step 17010: if the original volume is registered in theexternal storage subsystem field in the volume information for thestorage subsystem 303, then it is judged that the original volume isusing the external volume mapping program. Also, when judging whether ornot the original volume using the volume mapping program is registeredin the host computer, the volume number and the FC interface number arenot read from the original volume, but rather they are read from thevolume number and the FC interface number of the storage subsystem whichhas the external volume mapping program.

Below, explanations will be given regarding specific examples of thereevaluation and transfer of the volume 3412 and the volume 3411 in thestorage subsystem 301.

Concrete Example 1 of Reevaluation and Transfer of Volume in PresentEmbodiment

The management computer 600 starts the reevaluation of the volume 3412,which is in the first line of the volume information 385 (step 16020).

First, the management computer 600 references the value of the hintinformation AccessBandwidthHint for the volume 3412. The value of theAccessBandwidthHint is “10”.

Then, when the management computer 600 finds that “10” is the valuedefined for the AccessBandwidthHint of the storage subsystem 326 and thestorage subsystem 327 from the storage subsystem 301 and the storagesubsystem 303, it is clear that the storage subsystem 301 has abandwidth of 2 Gbps, but the storage subsystem 303 has an acceleratedbandwidth of 10 Gbps (step 16060).

Therefore, for the volume 3412 in the storage subsystem 301, instead ofproviding the external volume to the host as the external storagesubsystem via the storage subsystem 303, the volume itself can bemigrated to the storage subsystem 303 in order to fully capitalize onthe 10-Gbps bandwidth (step 16060). Therefore, the storage subsystem 303is specified as a transfer destination candidate. Then, the processingon the selected hint information is considered complete (step 16090),and the volume is evaluated with respect to the next hint (step 16040).

Then, the management computer 600 references the value defined for thehint information StorageCostHint for the volume 3412. The value in theStorageCostHint is “0”. Therefore, the volume does not have to bereevaluated with respect to this hint information.

Finally, the management computer 600 references the value defined forthe hint information DataAvailabilityHint for the volume 3412. The valuefor the DataAvailabilityHint is “10”.

Next, the management computer 600 references the value defined for theavailability in the case where “10” is defined for theDataAvailabilityHint values in the storage subsystem characteristics326, 327 received from both the storage subsystem 301 and the storagesubsystem 303. The availability for the storage subsystem 301 is“99.9%”, but the availability for the storage subsystem 303 is “99.999%”(step 16060). By migrating the volume itself to the storage subsystem303, the availability can be improved to provide a higher-performancevolume (step 16070). Therefore, the storage subsystem 303 is determinedas the transfer destination candidate. Then, the processing isconsidered complete for the selected hint information (step 16090), andall of the hint information in the volume information has beenreferenced. Therefore, the evaluation of the volume ends.

The foregoing evaluation produces a judgment that the bandwidth and theavailability of the volume 3412 can be improved by migrating it from thestorage subsystem 301 to the storage subsystem 303.

Therefore, the management computer 600 starts transferring the data. Inthe present embodiment, the processing from the evaluation to thetransfer is executed without seeking confirmation from theadministrator, however it is also possible to seek confirmation from theadministrator as in Embodiment 1.

Once it is determined that the data for the volume 3412 will be movedfrom the storage subsystem 301 to the storage subsystem 303, themanagement computer 600 then executes the volume migration program 624.

Since the volume 3412 is using the external volume mapping program, thevolume management table inside the host computer is not updated as instep 17030. Therefore, the volume management table in the host computer100 remains as shown in FIG. 11 without being changed.

Next, in order to transfer the volume 3412, the management computer 600creates the volume creation request based on the hint and the capacityallocated to the volume 3412, and then sends this request to the storagesubsystem 303.

The storage subsystem 303 executes the volume allocation program 330 andprepares the 200-GB volume 3439 that was requested. Since no FCinterface has been allocated to the volume 3439 at this point, “0” isallocated as the FC interface number (FIG. 10B). When the creation ofthe volume 3439 is complete, a notification of completion is sent fromthe storage subsystem 303 to the management computer.

The management computer 600 receives the notification from the storagesubsystem 303 indicating that the creation of the volume is complete,and then gives instructions to the volume migration means 700 of thestorage subsystem 303 to transfer the data in the volume 3412 to thevolume 3439. The volume migration means 700 copies the first blockthrough the last block of the volume 3412 into the volume 3439. In thepresent embodiment, the volume migration means is a program executed onthe storage subsystem, and the program is executed to perform copyingbetween volumes via the fiber channel 200.

When the copying into the volume 3439 is complete, the managementcomputer 600 updates the volume information 385 for the storagesubsystem 303 as shown in FIG. 10C. Here, the storage subsystem 303allocates the FC interface 3738 to the newly created volume 3439, andchanges the volume number to “3432”. This eliminates the necessity inEmbodiment 2 to rewrite the FC interface number and the volume number inthe volume management table 115 of the host computer 100, which wasnecessary in Embodiment 1 when performing a transfer.

Finally, the management computer 600 executes the volume release program612 to cause the volume 3412 in the storage subsystem 301 to becomeunallocated.

This completes the reevaluation of the volume 3412 and the volumetransfer processing which is performed based on the evaluation.

Concrete Example 2 of Reevaluation and Transfer of Volume in PresentEmbodiment

Next, the management computer 600 begins reevaluation of the volume3411, which is in the second line of the volume 385.

First, the management computer 600 references the value defined for thehint information AccessBandwidthHint for the volume 3411. The value ofthe AccessBandwidthHint is “1”. Then, the management computer 600references the value for when “10” is defined for the value of theAccessBandwidthHint of both the storage subsystem characteristics 326and the storage subsystem characteristics 327, which were received fromthe storage subsystem 301 and the storage subsystem 303. This clarifiesthat both of the storage subsystems have bandwidths of 1 Gbps.Therefore, it is not necessary to transfer the volume.

Next, the management computer 600 references the value defined for thehint information StorageCostHint for the volume 3411. The value definedfor the StorageCostHint is “10”. Then, the management computer 600references the bit unit price for when “10” is defined as the value ofthe StorageCostHint in both the storage subsystem characteristics 326and the storage subsystem characteristics 327, which were received fromthe storage subsystem 301 and the storage subsystem 303. The bit unitprice for the storage subsystem 301 is 2 ¢/MB, and the bit unit pricefor the storage subsystem 303 is 1 ¢/MB. Therefore, if the volume ismigrated to the storage subsystem 303, the bit unit price will rise, andso there is no advantage in migrating the volume.

Finally, the management computer 600 references the value defined forthe hint information DataAvailabilityHint for the volume 3411. Since thevalue of the DataAvailabilityHint is “0”, the reevaluation is notnecessary with respect to this hint.

The foregoing evaluation produces a determination that there is noadvantage or benefit in migrating the volume 3411 from the storagesubsystem 301 to the storage subsystem 303.

Therefore, the management computer 600 does not execute the volumemigration program 624 to transfer the volume 3411.

Embodiment 2 has been explained here as having the management computer600, similar to Embodiment 1. However, the programs which were providedin the management computer 600 in Embodiment 2 can also be provided tothe storage subsystem 303. These include: the configuration collectionprogram 605; the volume creation program 610; the volume release program612; the volume information obtaining program 620;the volume evaluatingprogram 622; and the volume migration program 624.

This configuration enables the storage subsystem 303 to check the FCinterfaces 3731-3736 regularly and to execute the sequence of proceduresto perform the reevaluation when the connection of the new storagesubsystem is detected.

Moreover, this reduces the burden on the network between the managementcomputer and the storage subsystem 303.

Finally, an explanation will be given regarding the volume migrationmeans 700, which is used in Embodiment 1 and Embodiment 2.

FIG. 20 shows a hardware structure diagram of the volume migration means700 shown in FIG. 1. The volume migration means 700 has: a CPU 710 forgoverning execution of the program; a memory 720 for storing the programand data necessary to execute the program; a network interface 730connected to the management network for sending and receiving data toand from the management computer 600; and a FC interface 750 for sendingand receiving data to and from the storage subsystem(s). The memory 720stores the volume copy program 740, which the volume migration means 700executes in accordance with instructions from the management computer600.

FIG. 21 shows the flow of the volume copy program 740 that is executedby the volume migration means 700 shown in FIG. 1. The CPU 710 of thevolume migration means 700 executes the volume copy program 740 storedin the memory 720.

First, the volume migration means 700 receives the original storagesubsystem and volume number, and the destination storage subsystem andthe volume number, from the management computer 600 as parameters forcopying the volume (step 21010).

Based on the parameters received at step 21010, the CPU 710 in thevolume migration means 700 copies the first block through the last blockin the original storage subsystem, into the destination storagesubsystem and volume, via the data network (step 21020).

More specifically, the CPU 710 first sends an SCSI “read” commandthrough the FC interface 750 to the volume in the original storagesubsystem, which is indicated in the parameters received at step 21010,and then reads the data from a block in the corresponding volume. Then,together with the data that is read here, the CPU 710 sends an SCSI“write” command through the FC interface 750 to the corresponding blockin the volume of the destination storage subsystem, which is indicatedin the parameters. When the destination storage subsystem receives the“write” command it writes the data into the corresponding volume block.The processing of the “read” command and the “write” command simplyneeds to be repeated from the first block to the last block in thevolume. The volume migration means 700 can store the data that is readhere into the memory 720, and it can read this data from the memory andsend it together with the “write” command to the destination storagesubsystem.

Although not represented in FIG. 21, when the CPU 710 executes step21020, it first confirms that the original storage subsystem and volumeand destination storage subsystem and volume are accessible from the FCinterface 750. If they are not accessible, then the volume copy program740 is cancelled and a notification is sent to the management computer600 to indicate that access cannot be achieved. When the managementcomputer 600 receives the notification it displays a warning on thedisplay 680 to the administrator urging him or her to change thesettings to enable access.

After the setting changes are performed, the administrator uses thekeyboard 682 and mouse 684 or other input to give an instruction, and,in response to this, the management computer 600 instructs the volumemigration means 700 to restart the volume copy program 740.

In the computer system shown in FIG. 2 in accordance with Embodiment 1,the volume migration means 700 is constituted by hardware which isindependent and different from the storage subsystem 301, the storagesubsystem 302, the host computer 100, and the management computer 600.This reduces the processing burden placed on the devices including thestorage subsystem, the host computer, and the management computer,particularly the management computer 600.

However, it is also possible to adopt a construction in which the volumecopy program 740 is provided to either the storage subsystem 301, thestorage subsystem 302, the host computer 100 or the management computer600, and that device executes the volume copy program 740, therebyachieving a construction in which the computer system does not includethe volume migration means 700 as an external device, such as shown inFIG. 20. If the volume copy program 740 is executed by the CPU 650 ofthe management computer 600, then the management computer 600 will havean FC interface (not shown in FIG. 9) for sending and receiving data toand from the storage subsystem over the data network, and this CPU 650will perform the processing shown in FIG. 21.

Furthermore, in the computer system shown in FIG. 9 according toEmbodiment 2, the volume migration means 700 is provided inside thestorage subsystem 303. However, the volume migration means 700 can beprovided to either the storage subsystem 301, the host computer 100 orthe management computer 600, either as software or as a hardwareconstruction. The volume migration means 700 can also be an externaldevice having an independent hardware construction.

The various embodiments described above alleviate the burden of resourceadministration for the administrator of a large storage system, in whichmultiple storage subsystems connected over a network have large amountsof storage volume allocated to them. For example, the burden ofdetermining how to transfer volume (volume) and other administrativeburdens is reduced.

Furthermore, volumes can be reevaluated. This reevaluation can beperformed based not only on maximum usage times (usage rates) determinedfor each storage subsystem individually and various types of access madeto the volumes, but also based on information which cannot be obtainedby measuring factors in real time, such as the reliability and/or costof the volume. Namely, the reevaluation of the volumes can also beperformed based on the “hints”, which are allocated to the volumes inadvance and cannot be measured in real time.

In a SAN or other computer system with multiple storage subsystems, theembodiments described in the present specification can provide a methodof detecting the addition of a storage subsystem or structural changesto storage subsystems on the SAN, to redistribute existing volumes basedon the “hints” given when the volumes are made, so as to manage thedistribution of the volume so that resources are utilized effectively.

1. A method of managing volumes of a plurality of storage systems, by amanagement computer connected via a network to the plurality of storagesystems having volumes connected to a computer via a network and storingdata used by the computer, the method comprising the steps of: keeping acorrespondence between a level indicating a specific performance of avolume, and storage system characteristics of the storage system;obtaining from a first storage system a level indicating a performanceof a volume allocated to the computer by the first storage system; andreferencing the storage system characteristics of the first storagesystem that corresponds to the obtained level indicating the performanceof the volume and storage system characteristics of another storagesystem, respectively, and comparing the performances of the volumes ofthe respective storage systems against each other.
 2. The volumemanagement method according to claim 1, wherein a correspondence isobtained from the storage system connected to the computer.
 3. Thevolume management method according to claim 1, wherein the comparison ofthe performances of the respective volumes in the respective storagesystems is performed when the correspondence is obtained from a newstorage system that has been connected to the management computer viathe network.
 4. The volume management method according to claim 2,wherein the comparison of the performances of the respective volumes isalso performed when a new correspondence is obtained from the storagesystem.
 5. The volume management method according to claim 1, whereinthe level is an integer value from 0 to
 10. 6. The volume managementmethod according to claim 1, further comprising the step of instructingthe other storage subsystem, based on the results of the comparison, toallocate to the computer a volume having storage system characteristicsof the other storage system corresponding to the obtained level.
 7. Thevolume management method according to claim 6, wherein the managementcomputer receives an input giving an instruction to allocate to thecomputer the volume having storage system characteristics of the otherstorage system corresponding to the obtained level, and instructs theallocation.
 8. The volume management method according to claim 1,wherein the comparison of respective levels indicating a specificperformance is not performed in a case where the level indicating thespecific performance of the volume indicates that the specificperformance is not needed.
 9. The volume management method according toclaim 6, further comprising the steps of: copying data stored in avolume of the first storage system into a volume allocated to thecomputer based on the instructions; and giving instructions to thecomputer via a management network to execute, via a data network, atleast one of: reading the data copied by the computer into the allocatedvolume, and writing new data.
 10. The volume management method accordingto claim 1, wherein, in a case where there are a plurality of specificperformances, the comparison is performed using the highest level ofperformance.
 11. A method of managing a volume of a first storage systemconnected to a computer via a network, and a volume of a second storagesystem connected to the first storage system, by a management computerconnected to the first storage system and the second storage system viaa network, the method comprising the steps of: keeping a correspondencebetween a level indicating a specific performance of a volume andstorage system characteristics indicating a performance of the storagesystem, for each of the storage systems; obtaining a level indicating aspecific performance of a volume of the first storage system, and alevel indicating a specific performance of a volume of the secondstorage system connected to the volume of the first storage system;comparing the storage system characteristics corresponding to theobtained level; and storing data stored in the volume of the secondstorage system into the volume of the first storage system, based on theresults of the comparison.
 12. The volume management method according toclaim 11, wherein the comparison of the storage system characteristicsis performed by obtaining mapping information indicating that the volumeof the first storage system is connected to the volume of the secondstorage system, based on the mapping information.
 13. The volumemanagement method according to claim 12, wherein the mapping informationis obtained from the first storage system.
 14. The volume managementmethod according to claim 12, further comprising the step of, when theresults of the comparison indicate that the storage systemcharacteristics of the first storage system corresponding to the levelindicating the specific performance of the volume of the second storagesystem is better than the storage system characteristics of the secondstorage system, storing the data into the volume having a specificperformance, based on the storage system characteristics of the firststorage system corresponding to the level of the first storage system.15. The volume management method according to claim 14, furthercomprising the step of instructing the first storage system to erase themapping information.
 16. A first storage system connected to a computervia a network, comprising: a volume connected to a volume of anotherstorage system storing data used by a computer; a memory for keeping acorrespondence between a level indicating a specific performance of thevolume, and storage system characteristics of the storage system, foreach of the storage systems; and a control unit for controlling accessmade to the first storage system or the other storage system from thecomputer, wherein the control unit obtains the level indicating thespecific performance of the volume of the other storage system,references the storage system characteristics of the first storagesystem and the other storage system corresponding to the level based onthe correspondence, and compares the referenced values.
 17. The firststorage system according to claim 16, wherein based on the result of thecomparison, the data is stored into a volume having the storage systemcharacteristics corresponding to the level indicating the specificperformance of the volume of the first storage system.
 18. A storagemedium storing a program that can be read by a computer managing volumesof a plurality of storage systems, which program is executed by amanagement computer connected via a network to the plurality of storagesystems having volumes that are connected to a computer and to theplurality of storage systems to store data used by the computer, thestorage medium comprising: a sequence of obtaining correspondencesbetween levels indicating a specific performance of volume, and storagesystem characteristics of the storage system; a sequence of obtainingfrom a first storage system a level indicating a performance of a volumeallocated to the computer by the first storage system; and referencingthe storage system characteristics of the first storage systemcorresponding to the obtained level indicating the performance of thevolume, and storage system characteristics of another storage system,and comparing the performances of the volumes of the respective storagesystems against each other.
 19. The storage medium according to claim18, further comprising a sequence of giving an instruction to the otherstorage system based on the results of the comparison, to allocate tothe computer a volume of the other storage system having storage systemcharacteristics corresponding to the obtained level.
 20. A computersystem comprising a plurality of storage systems having a volume storingdata used by a host computer, and a management computer connected to thestorage systems via a network, wherein the management computercomprises: a CPU for performing processing based on information receivedfrom the storage systems; and a management network interface for sendingrequests to the storage systems and receiving responses from the storagesystems, and each storage system comprises: a memory for acorrespondence between a level indicating a specific performance of thevolume and a value of the performance of the storage system; and a levelindicating a performance of the volume of the storage system; a volumeallocation unit for referencing the correspondence and allocating to thehost computer a volume having the performance value corresponding to thelevel indicating the specific performance requested by the managementcomputer; and a network interface for sending and receiving data to andfrom the management computer, wherein, when the CPU of the managementcomputer detects a storage system connected to the network interfacewhich is connected via the network to the management network interface,the CPU obtains the correspondence from the storage system, obtains thelevel indicating the performance of the volume which the CPU alreadyallocated to the host computer, references the correspondences of theplurality of storage systems, compares the storage systemcharacteristics of the plurality of storage systems corresponding to thelevel, and based on the result of the comparison, gives an instructionto a different storage system from the storage system having the volumethat is already allocated to the host computer, to allocate a volumecorresponding to the level; and the storage system volume allocationunit allocates to the host computer a volume having the performancecorresponding to the level based on the allocation instruction.